Poly(vinyl butyral) (PVB) is commonly used in the manufacture of polymer sheets that can be used as interlayers in light-transmitting laminates such as safety glass or polymeric laminates. Safety glass typically refers to a transparent laminate comprising a poly(vinyl butyral) sheet disposed between two panes of glass. Safety glass is often used to provide a transparent barrier in architectural and automotive openings. Its main function is to absorb energy, such as that caused by a blow from an object, without allowing penetration through the opening.
In many applications it is desirable to use only a single pane of glass onto which one or more layers of polymeric material are disposed to produce a multiple pane glass panel. In one simple form, a two layer poly(vinyl butyral)/polyester construct is disposed on a pane of glass with the poly(vinyl butyral) in contact with the glass, and the three layer panel is then laminated to produce a finished multiple layer glass panel, which is also known as a bilayer.
Such bilayers, however, are prone to delamination if subjected to certain environmental conditions, including the ingress of moisture through the polyester and into the poly(vinyl butyral). The ingress of water into the poly(vinyl butyral) layer can lead to delamination of the entire panel because the adhesion properties of the poly(vinyl butyral) are detrimentally impacted by increased water content.
Attempts to alleviate moisture ingress have included the use of poly(vinyl butyral) rather than polyurethane, the inclusion of additives into the poly(vinyl butyral) layer, and the specific adjustment of the molecular properties of the poly(vinyl butyral) to create a layer that is less prone to absorption and retention of water. These attempts have all resulted in varying degrees of success.
Accordingly, further improved compositions and methods of manufacture for improved multiple layer glass units having an exposed plastic surface are desired.